The Nuclear Atom, Periodic Table, and Chemical Formulas

Flashcards reviewing key concepts of the nuclear atom, subatomic particles, isotopes, ions, chemical formulas, and periodic table trends.

What is an atom?

An atom is the basic unit of an element.

What are the charge, mass, and location of protons, neutrons, and electrons?

Protons have a positive charge, a mass of $1\,\text{amu}$, and are located in the nucleus. Neutrons have $0$ charge, a mass of $1\,\text{amu}$, and are located in the nucleus. Electrons have a negative charge, a mass of $0\,\text{amu}$, and are located outside the nucleus.

What defines an element, and what determines its identity?

An element is a substance made of only one type of atom. The number of protons determines the element (e.g., Hydrogen has 1 proton with atomic # 1, Carbon has 6 protons with atomic # 6, and Oxygen has 8 protons with atomic # 8).

What are isotopes?

Isotopes are atoms of the same element with the same number of protons but a different number of neutrons (e.g., Carbon-12 has 6 protons and 6 neutrons, while Carbon-14 has 6 protons and 8 neutrons).

How are cations and anions formed?

Cations are formed when atoms lose one or more electrons, giving them a positive charge. Anions are formed when atoms gain one or more electrons, giving them a negative charge.

What formula is used to calculate average atomic mass?

$$\text{Average atomic mass} = \sum (\text{fractional abundance} \times \text{isotope mass})$$

What information do chemical formulas and chemical symbols convey?

Chemical formulas show which elements are present and the number or ratio of atoms or ions present. Capital letters signal the start of an element symbol, while lowercase letters are part of a two-letter symbol (e.g., $Co$ is Cobalt, whereas $CO$ represents Carbon and Oxygen).

What is the difference between a molecular formula and an empirical formula?

A molecular formula shows the exact number of each type of atom in a molecule (e.g., $C_6H_{12}O_6$), whereas an empirical formula gives the simplest whole-number ratio of elements in a compound (e.g., $CH_2O$).

How is the periodic table organized into periods and groups?

The periodic table organizes elements by increasing atomic number. Periods are the 7 horizontal rows whose elements share the same number of electron shells or energy levels. Groups are the 18 vertical columns whose elements share similar chemical properties.

What are the key characteristics and locations of metals, non-metals, and metalloids?

Metals are mostly on the left, good conductors of heat and electricity, shiny, and malleable. Non-metals are mostly on the right, poor conductors, and many are gases. Metalloids lie along the stair-step and have properties of both metals and non-metals.

What are the characteristics and group numbers of Alkali metals, Alkaline earth metals, Halogens, and Noble gases?

Group 1 contains Alkali metals (very reactive metals), Group 2 contains Alkaline earth metals (reactive metals), Group 17 contains Halogens (very reactive non-metals), and Group 18 contains Noble gases (very stable and unreactive non-metals like He, Ne, Ar).

What is the difference between atomic number, mass number, and average atomic mass?

Atomic number is the number of protons in an atom. Mass number is the total number of protons plus neutrons ($\text{Mass number} = \text{protons} + \text{neutrons}$). Average atomic mass is the weighted average of the masses of an element's isotopes.